大直径超长桩后继打桩拒锤现象分析及单桩承载力计算-中国烟草学报.PDF

第 27 卷 增 2 岩石力学与工程学报 Vol.27 Supp.2 2008 年 9 月 Chinese Journal of Rock Mechanics and Engineering Sept. ，2008 大直径超长桩后继打桩拒锤现象分析 及单桩承载力计算 刘 润，闫 玥，闫澍旺 (天津大学 建筑工程学院，天津 300072) 摘要：受到海上施工条件的限制，特别是大直径超长桩的施工常出现停锤，停锤后继续打桩时，连续打桩引起的 桩周地基土中的超静孔隙水压力消散，土体强度得到恢复和提高，使得打桩阻力增大，甚至出现拒锤现象。分析 表明，地基土层的分布、土体中裂缝的开展、停打时间的长短以及桩管内土塞的作用直接影响土体强度的恢复和 提高程度。提出超静孔隙水压力的计算方法以及超静孔隙水压力的时间效应；结合一维应力波动理论，以实测打 桩记录为依据，采用反分析方法确定当后继打桩出现拒锤现象时的单桩承载力。实际工程算例和海上原位动测结 果表明，该方法具有可行性。 关键词：桩基工程；打桩分析；拒锤；强度增长；单桩承载力 中图分类号：TU 473 文献标识码：A 文章编号：1000 –6915(2008)增 2 –3459 –06 STUDY ON REFUSAL OF RESTARTING OF LARGE DIAMETER AND DEEP PENETRATION PILE AND BEARING CAPACITY CALCULATION LIU Run ，YAN Yue ，YAN Shuwang (College of Civil Engineering，Tianjin University，Tianjin 300072，China) Abstract ：Due to the harsh environmental conditions in ocean engineering ，intermissions occur during the driving of large diameter and deep penetration piles，which may cause difficulties ，even refusal，in re-starting the pile. Analytical results show that soil strength recovering is influenced by the soil stratum distribution ，the crack development around the pile，the cessation time of driving and the soil plug effect in the pile pipe. A calculation method is proposed to identify the developed excess pore water pressure and its time effects in the soil around the pile during driving. Based on the driving records ，the back-figured method is applied to estimate the pile bearing capacity after refusal taking place. The calculated results agree well with the in-situ observed data，which indicates that the proposed back-figured procedure can be used in similar pile driving situations. Key words ：pile